yancat.c restructuring

This is larger changeset adjusting how we spawn threads and processes.
Instead of the reading process being also the controller, we add
separate arbiter than can overview spawnees (currently reader and
writer).

This is much cleaner approach.
shmw_sysv: trivial changes
buffer: avoid _ in global namespace
yancat, buffer: trivial changes and comments
shmw_malloc: make sure buffer is aligned on page boundary
fdpack: add close() virtuals

We separate dtor and from close with this change.

Also few trivial changes.
yancat: use fd_close() in task functions
common: XSI strerror_r wrapper (commented out)

As we use gnu variant.
common: add TFR and DEBL macros
fdpack: move socket opening

From ctor to open.
yancat: signal updates

Especially for threading scenarios.
yancat: update year
README: tiny update
buffer: add buf_forcefetch_w()

Useful when we need to operate safely on fetched data (e.g. in writer
epilogue).
yancat: move fds ctors/dtors outside main loop
yancat: update pid handling
yancat: update writer_epi / DEB use fix

Use forcefetch and allow looping even with failed block writes.
Fix DEB use in one place.
comments
yancat: split done into abrt+done

This lets us avoid cmpxchg that older gccs don't support.
common.h: add DEB2